With the rapid development of the information technology, the electronic products such as portable electronic products, e.g. notebook computer, cell phone, and tablet computer, are widely used. Since these portable electronic products may be carried and utilized by the user anytime and anywhere for the purpose of mass data transmission between these portable electronic products by device interconnections, thus there is a need to connect a portable electronic product to a host unit such that the host unit is capable of supplying the power to the portable electronic product via the USB connection and performs data transmission therebetween using USB protocol. However, conventionally, when a portable electronic product is connected to the host unit via an electrical connector, the host unit detect whether the portable electronic product is inserted to the USB port of the host unit by using a contact pin of the electrical connector. Further, the contact pin is not a standard hardware component of the USB connector, result in the inconvenient utilization between the portable electronic product and the host unit. More over, if the portable electronic product is connected to the host unit by a USB extension wire, the host unit malfunctions to supply the power to the portable electronic product with the high power consumption. Consequently, there is a need to develop a novel detecting system and method to solve the aforementioned problems.